The primary methods utilized to identify tannery operations and evaluate their current conditions involved historical research with multiple follow-up site visits to document relevant features. Research consisted of reviewing historical maps in microfiche and paper formats, reviewing text-format historical records, and in some cases following anecdotal reports provided by Wilmington residents. Numerous tanneries identified during research proved to be overlapping or related tannery operations. Overlapping and duplicate tannery information was sorted and grouped during this investigation. During field visits to each site, information was collected via visual inspection, digital photography, and measurements of exposed soil/grass at selected sites.

The techniques used to identify tanneries varied by information source. Multiple information sources were united in a common database and Geographic Information System (GIS) that organized relevant information. Separate tables were used to collect data on historical findings, details of the field investigation, site photos, and land parcel data from New Castle County/First American Real Estate Solutions. The methods used in collecting and ranking these data will be discussed by task in this chapter.